It is well known for decades that if a receiver of radio device, e.g., a wireless BS or AP (hereafter all referred to as BS), can effectively cancel the received radio signal from a transmitter located on the same device (referred to as self-interference) or from a nearby radio device, the radio device can simultaneously transmit and receive radio signals in the same frequency channel, assuming noise and other interferences are sufficiently lower than the intended signal to be received. Various methods for canceling the self-interference have been known, e.g. in references [1] [2] [3] [4]. Prior arts suffer from insufficient cancelation of self-interference, and often leave too much remaining self-interference after cancelation, especially when the transmitted power is high. We invented a new method and circuits for self-interference cancelation that offers significantly better performance than prior arts, thus, enabling practical Single Channel Full Duplex (SCFD) radios that were previously not feasible.